The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-var...The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-varying meshing stiffness.Based on dynamic theory of the gear system,a dynamic model of the planetary gear train was established.The lubrication performances of modified gear systems under vibrations and static loads were analyzed.Compared with other transmission types,the best lubrication effect could be produced by the positive transmission.A thicker lubricating oil film could be formed,and the friction coefficient and oil film flash temperature are the smallest.Increasing modification coefficient improves the lubrication performance continuously but intensifies the engage-in and tooth-change impact.For the planetary and inner gears,the increase in the modification coefficient also leads a decrease in the oil film stiffness.展开更多
The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment, which realizes the nmlti-motion modes of the autonomous underwater vehicle （AUV） such as vectored thruster and wheele...The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment, which realizes the nmlti-motion modes of the autonomous underwater vehicle （AUV） such as vectored thruster and wheeled movement. In order to study the interactional principle between the hull and the wheel propellers while the AUV navigating in water, the computational fluid dynamics （CFD） method is used to simulate numerically the unsteady viscous flow around AUV with propellers by using the Reynolds-averaged Navier-Stokes （RANS） equations, shear-stress transport （SST） k-w model and pressure with splitting of operators （PISO） algorithm based on sliding mesh. The hydrodynamic parameters of AUV with propellers such as resistance, pressure and velocity are got, which reflect well the real ambient flow field of AUV with propellers. Then, the semi-implicit method for pressure-linked equations （SIMPLE） algorithm is used to compute the steady viscous flow field of AUV hull and propellers, respectively. The computational results agree well with the experimental data, which shows that the numerical method has good accuracy in the prediction of hydrodynamic performance. The interaction between AUV hull and wheel propellers is predicted qualitatively and quantitatively by comparing the hydrodynamic parameters such as resistance, pressure and velocity with those from integral computation and partial computation of the viscous flow around AUV with propellers, which provides an effective reference to the shady on noise and vibration of AUV hull and propellers in real environment. It also provides technical support for the design of new AUVs.展开更多
The effect of pre-recovery on the recrystallization kinetics of a supersaturated Al–Mn alloy annealed at 530°C was investigated.The results show that the pre-recovery treatment can lead to faster recrystallizati...The effect of pre-recovery on the recrystallization kinetics of a supersaturated Al–Mn alloy annealed at 530°C was investigated.The results show that the pre-recovery treatment can lead to faster recrystallization kinetics at the initial stage but cause sluggish recrystallization at the later stage.This different recrystallization behavior is explained by the formation of precipitates-free zones and the consumption of driving force during the pre-recovery treatment.The promoted recrystallization at the early stage can be interpreted by the promotion of recrystallization nucleation through sub-grain growth to a critical size inside precipitates-free zones.A simple model is presented to describe the nucleation of recrystallization with pre-recovery treatment in the supersaturated Al–Mn alloys.展开更多
An OpenMP approach was proposed to parallelize the sequential molecular dynamics(MD) code on shared memory machines. When a code is converted from the sequential form to the parallel form, data dependence is a main pr...An OpenMP approach was proposed to parallelize the sequential molecular dynamics(MD) code on shared memory machines. When a code is converted from the sequential form to the parallel form, data dependence is a main problem. A traditional sequential molecular dynamics code is anatomized to find the data dependence segments in it, and the two different methods, i.e., recover method and backward mapping method were used to eliminate those data dependencies in order to realize the parallelization of this sequential MD code. The performance of the parallelized MD code was analyzed by using some performance analysis tools. The results of the test show that the computing size of this code increases sharply form 1 million atoms before parallelization to 20 million atoms after parallelization, and the wall clock during computing is reduced largely. Some hot-spots in this code are found and optimized by improved algorithm. The efficiency of parallel computing is 30% higher than that of before, and the calculation time is saved and larger scale calculation problems are solved.展开更多
The dynamic mechanical properties of rock specimens after thermal treatment in the air-filled environment(AE:i.e.,at the free surface)have been extensively investigated,yet they are rarely estimated in the quasi-vacuu...The dynamic mechanical properties of rock specimens after thermal treatment in the air-filled environment(AE:i.e.,at the free surface)have been extensively investigated,yet they are rarely estimated in the quasi-vacuum environment(VE:i.e.,far from free surface),which is of special importance in engineering practice.Several precise laboratory tests(i.e.,split Hopkinson pressure bar test)on marble samples in both AE and VE were performed to investigate physical and dynamic mechanical behaviors of marble after heat treatment(25℃ to 900℃)in AE and VE.The tests results demonstrate that related properties of marble could be divided into three different stages by corresponding critical temperatures of 300℃ and 600℃,at which heat damage factors are 0.29(0.30)and 0.88(0.92)in VE(AE),respectively.The thermal damage developes more fully in AE than in VE.The thermal environment plays an important role,especially in Stage 3.Specifically,a conspicuous difference(greater than 20%)between AE and VE occurs in corresponding dynamic strength and the anti-deformation capacities of tested marble specimen.The influence of heat damage of rock is very important and valuable in engineering practice,particularly when the temperature is very high(greater than 600℃).展开更多
The kinetic behavior of leaching copper from low grade copper oxide ore was investigated. The effects of leaching temperature, H2SO4 concentration, particle size of crude ore and agitation rate on the leaching efficie...The kinetic behavior of leaching copper from low grade copper oxide ore was investigated. The effects of leaching temperature, H2SO4 concentration, particle size of crude ore and agitation rate on the leaching efficiency of copper were also evaluated. And the kinetic equations of the leaching process were obtained. The results show that the leaching process can be described with a reaction model of shrinking core. The reaction can be divided into three stages. The first stage is the dissolution of free copper oxide and copper oxide wrapped by hematite-limonite ore. At this stage, the leaching efficiency is very fast （leaching efficiency is larger than 60%）. The second stage is the leaching of diffiuent copper oxides, whose apparent activation energy is 43.26 kJ/mol. During this process, the chemical reaction is the control step, and the reaction order of H2SO4 is 0.433 84. The third stage is the leaching of copper oxide wrapped by hematite-limonite and silicate ore with apparent activation energy of 16.08 kJ/mol, which belongs to the mixed control.展开更多
The effect of Li(2.0 wt%)addition on mechanical properties and ageing precipitation behavior of Al-3.0 Mg 0.5 Si was investigated by tensile test,dynamic elasticity modulus test,scanning electron microscopy(SEM),trans...The effect of Li(2.0 wt%)addition on mechanical properties and ageing precipitation behavior of Al-3.0 Mg 0.5 Si was investigated by tensile test,dynamic elasticity modulus test,scanning electron microscopy(SEM),transmission electron microscopy(TEM)and high-resolution transmission electron microscopy(HRTEM)images.The results show that the tensile strength of the Li-containing alloy can be significantly improved;however,the ductility is sharply decreased and the fracture mechanism changes from ductile fracture to intergranular fracture.The elasticity modulus of the Li-containing alloy increases by 11.6%compared with the base alloy.The microstructure observation shows that the Li addition can absolutely change the precipitation behavior of the base alloy,andδ′-Al_(3)Li phase becomes the main precipitates.Besides,β′′-Mg_(2)Si andδ′-Al_(3)Li dual phases precipitation can be visibly observed at 170℃ ageing for 100 h,although the quantity ofδ′-Al_(3)Li phase is more thanβ′′-Mg_(2)Si phase.The width of the precipitate-free zone(PFZ)of the Li-containing alloy is much wider at the over-ageing state than the base alloy,which has a negative impact on the ductile and results in the decrease of elongation.展开更多
The effect of T6I6 treatment on the dynamic mechanical and microstructure behaviour of Al-Si-Mg-Cu cast alloy was investigated using split Hopkinson pressure bar(SHPB), transmission electron microscopy(TEM), and highr...The effect of T6I6 treatment on the dynamic mechanical and microstructure behaviour of Al-Si-Mg-Cu cast alloy was investigated using split Hopkinson pressure bar(SHPB), transmission electron microscopy(TEM), and highresolution transmission electron microscopy(HRTEM). Besides, the impact resistances of T6I6 and T6 motor shells of new energy vehicles made of Al-Si-Mg-Cu cast alloy were compared using a trolley crash test. The results indicated that the main strengthening-phases of the T6 peak-aged and T6I6 peak-aged alloy were GP zone and β″ precipitates. T6I6treatment can increase the density and size of β″ precipitates in peak-aged alloy and enhance both its tensile strength(σb)and elongation(δ). The dynamic toughness values of T6I6 samples are 50.34 MJ/m^(3) at 2000 s^(-1) and 177.34 MJ/m^(3) at 5000 s^(-1) which are 20% and 12% higher than those of T6 samples, respectively. Compared with a T6 shell, the overall deformation of T6I6 shell is more uniform during the crash test. At an impact momentum of 3.5×10;kg·m/s, the T6I6shell breaks down at 0.38 s which is 0.10 s later than the T6 shell.展开更多
Effects of strain rate and water-to-cement ratio on the dynamic compressive mechanical behavior of cement mortar are investigated by split Hopkinson pressure bar(SHPB) tests. 124 specimens are subjected to dynamic uni...Effects of strain rate and water-to-cement ratio on the dynamic compressive mechanical behavior of cement mortar are investigated by split Hopkinson pressure bar(SHPB) tests. 124 specimens are subjected to dynamic uniaxial compressive loadings.Strain rate sensitivity of the materials is measured in terms of failure modes, stress-strain curves, compressive strength, dynamic increase factor(DIF) and critical strain at peak stress. A significant change in the stress-strain response of the materials with each order of magnitude increase in strain rate is clearly seen from test results. The slope of the stress-strain curve after peak value for low water-to-cement ratio is steeper than that of high water-to-cement ratio mortar. The compressive strength increases with increasing strain rate. With increase in strain rate, the dynamic increase factor(DIF) increases. However, this increase in DIF with increase in strain rate does not appear to be a function of the water-to-cement ratio. The critical compressive strain increases with the strain rate.展开更多
The desorption test was conducted to evaluate the desorption behavior of Pb(Ⅱ)and Cd(Ⅱ)using citric acid.The influential factors that were considered included initial Pb(Ⅱ),Cd(Ⅱ)contamination levels in soil,concen...The desorption test was conducted to evaluate the desorption behavior of Pb(Ⅱ)and Cd(Ⅱ)using citric acid.The influential factors that were considered included initial Pb(Ⅱ),Cd(Ⅱ)contamination levels in soil,concentration of citric acid,reaction time,soil pH value and ionic strength.The test results indicated that the desorption was a rapid reaction(less than 6 h),and the removal percentages of Cd(Ⅱ)and Pb(Ⅱ)increased with the increasing contamination levels,concentration of citric acid and the addition of Na^+,Ca^(2+),Na^+, Cl~– and the chelating of organic ligands.展开更多
To improve the performance of chaotic secure communication,three simplified chaotic systems with one variable parameter were investigated.Basic properties were analyzed including symmetry,dissipation and topological s...To improve the performance of chaotic secure communication,three simplified chaotic systems with one variable parameter were investigated.Basic properties were analyzed including symmetry,dissipation and topological structure.Complex dynamical behaviors of the systems including chaos and periodic orbits were verified by numerical simulations,Lyapunov exponents and bifurcation diagrams.Interestingly,the three systems were integrated in a common circuit,and their dynamical behaviors were easily observed by adjusting regulable resistors R28,R14 and R17,respectively,and the relations between the variable resistor and the system parameter were deduced.The circuit experiment results agree well with the simulation results.Finally,a secure communication scheme based on chaos shift keying(CSK) was presented,which lays an experiment foundation for chaotic digital secure communication.展开更多
Composite wing static aeroelasticity was analyzed through a loosely coupled method and the effects on composite wing characteristics under different flight attitudes were presented. Structural analysis and aerodynamic...Composite wing static aeroelasticity was analyzed through a loosely coupled method and the effects on composite wing characteristics under different flight attitudes were presented. Structural analysis and aerodynamic analysis were carried out through finite element method (FEM) software NASTRAN and computational fluid dynamics (CFD) software FLUENT, respectively. Correlative data transfer and mesh regenerate procedure were applied to couple the results of computational structure dynamics (CSD) and CFD. After static aeroelasticity analysis under different flight attitudes, it can be seen that lift increases with the increase of flight speed and the incremental value enlarges gradually in both rigid and elastic wings. Lift presents a linear increment relationship with the increase of attack angle when the flight speed is 0.4Ma or 0.6Ma, but nonlinear increment in elastic wing when flight speed is 0.8Ma. On the effect of aeroelasticity, the maximum of deformation increases with the increase of flight speed and attack angle, and the incremental value decreases with the increase of flight speed while uniform with different attack angles. The results provide a reference for engineering applications.展开更多
The glass formation was intensively studied for Fe-based alloys. Parameters defining kinetics and thermodynamic behavior of crystallization were calculated using calorimetric measurements and physical properties of co...The glass formation was intensively studied for Fe-based alloys. Parameters defining kinetics and thermodynamic behavior of crystallization were calculated using calorimetric measurements and physical properties of constituent elements. It is found that the critical cooling rate Rc estimated by combining kinetic and thermodynamic parameters highly correlates with measured Rc found in literatures with correlation coefficient R2=0.944, and alloy compositions with high melting enthalpy AHm can easily form glass even without high undercooling and high value of the ,β-parameter of Tumbull＇s theory, revealing that the glass formation in this group of alloys is mostly controlled by growth limitation. This combination of kinetic and thermodynamic parameters can be used to determine alloy composition with good glass forming ability in Fe-based alloys just using physical properties of alloying elements and calorimetric measurements.展开更多
Autonomous underwater vehicles （AUVs） navigating on the sea surface are usually required to complete the communication tasks in complex sea conditions. The movement forms and flow field characteristics of a multi-mo...Autonomous underwater vehicles （AUVs） navigating on the sea surface are usually required to complete the communication tasks in complex sea conditions. The movement forms and flow field characteristics of a multi-moving state AUV navigating in head sea at high speed were studied. The mathematical model on longitudinal motion of the high-speed AUV in head sea was established with considering the hydrodynamic lift based on strip theory, which was solved to get the heave and pitch of the AUV by Gaussian elimination method. Based on this, computational fluid dynamics （CFD） method was used to establish the mathematical model of the unsteady viscous flow around the AUV with considering free surface effort by using the Reynolds-averaged Navier-Stokes （RANS） equations, shear-stress transport （SST） k-w model and volume of fluid （VOF） model. The three-dimensional numerical wave in the computational field was realized through defining the unsteady inlet boundary condition. The motion forms of the AUV navigating in head sea at high speed were carried out by the program source code of user-defined function （UDF） based on dynamic mesh. The hydrodynamic parameters of the AUV such as drag, lift, pitch torque, velocity, pressure and wave profile were got, which reflect well the real ambient flow field of the AUV navigating in head sea at high speed. The computational wave profile agrees well with the experimental phenomenon of a wave-piercing surface vehicle. The force law of the AUV under the impacts of waves was analyzed qualitatively and quantitatively, which provides an effective theoretical guidance and technical support for the dynamics research and shape design of the AUV in real complex environnaent.展开更多
基金Projects(51575289,51705270)supported by the National Natural Science Foundation of China。
文摘The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-varying meshing stiffness.Based on dynamic theory of the gear system,a dynamic model of the planetary gear train was established.The lubrication performances of modified gear systems under vibrations and static loads were analyzed.Compared with other transmission types,the best lubrication effect could be produced by the positive transmission.A thicker lubricating oil film could be formed,and the friction coefficient and oil film flash temperature are the smallest.Increasing modification coefficient improves the lubrication performance continuously but intensifies the engage-in and tooth-change impact.For the planetary and inner gears,the increase in the modification coefficient also leads a decrease in the oil film stiffness.
基金Project(2006AA09Z235) supported by National High Technology Research and Development Program of ChinaProject(CX2009B003) supported by Hunan Provincial Innovation Foundation For Postgraduate,China
文摘The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment, which realizes the nmlti-motion modes of the autonomous underwater vehicle （AUV） such as vectored thruster and wheeled movement. In order to study the interactional principle between the hull and the wheel propellers while the AUV navigating in water, the computational fluid dynamics （CFD） method is used to simulate numerically the unsteady viscous flow around AUV with propellers by using the Reynolds-averaged Navier-Stokes （RANS） equations, shear-stress transport （SST） k-w model and pressure with splitting of operators （PISO） algorithm based on sliding mesh. The hydrodynamic parameters of AUV with propellers such as resistance, pressure and velocity are got, which reflect well the real ambient flow field of AUV with propellers. Then, the semi-implicit method for pressure-linked equations （SIMPLE） algorithm is used to compute the steady viscous flow field of AUV hull and propellers, respectively. The computational results agree well with the experimental data, which shows that the numerical method has good accuracy in the prediction of hydrodynamic performance. The interaction between AUV hull and wheel propellers is predicted qualitatively and quantitatively by comparing the hydrodynamic parameters such as resistance, pressure and velocity with those from integral computation and partial computation of the viscous flow around AUV with propellers, which provides an effective reference to the shady on noise and vibration of AUV hull and propellers in real environment. It also provides technical support for the design of new AUVs.
基金Project(2016YFB0300901)supported by National Key R&D Program of ChinaProject(51421001)supported by the National Natural Science Foundation of ChinaProject(106112015CDJXY130003)supported by the Fundamental Research Funds for the Central Universities,China
文摘The effect of pre-recovery on the recrystallization kinetics of a supersaturated Al–Mn alloy annealed at 530°C was investigated.The results show that the pre-recovery treatment can lead to faster recrystallization kinetics at the initial stage but cause sluggish recrystallization at the later stage.This different recrystallization behavior is explained by the formation of precipitates-free zones and the consumption of driving force during the pre-recovery treatment.The promoted recrystallization at the early stage can be interpreted by the promotion of recrystallization nucleation through sub-grain growth to a critical size inside precipitates-free zones.A simple model is presented to describe the nucleation of recrystallization with pre-recovery treatment in the supersaturated Al–Mn alloys.
基金Project (50371026) supported by the National Natural Science Foundation of China
文摘An OpenMP approach was proposed to parallelize the sequential molecular dynamics(MD) code on shared memory machines. When a code is converted from the sequential form to the parallel form, data dependence is a main problem. A traditional sequential molecular dynamics code is anatomized to find the data dependence segments in it, and the two different methods, i.e., recover method and backward mapping method were used to eliminate those data dependencies in order to realize the parallelization of this sequential MD code. The performance of the parallelized MD code was analyzed by using some performance analysis tools. The results of the test show that the computing size of this code increases sharply form 1 million atoms before parallelization to 20 million atoms after parallelization, and the wall clock during computing is reduced largely. Some hot-spots in this code are found and optimized by improved algorithm. The efficiency of parallel computing is 30% higher than that of before, and the calculation time is saved and larger scale calculation problems are solved.
基金Projects(51579239,42077240,51979280)supported by the National Natural Science Foundation of China。
文摘The dynamic mechanical properties of rock specimens after thermal treatment in the air-filled environment(AE:i.e.,at the free surface)have been extensively investigated,yet they are rarely estimated in the quasi-vacuum environment(VE:i.e.,far from free surface),which is of special importance in engineering practice.Several precise laboratory tests(i.e.,split Hopkinson pressure bar test)on marble samples in both AE and VE were performed to investigate physical and dynamic mechanical behaviors of marble after heat treatment(25℃ to 900℃)in AE and VE.The tests results demonstrate that related properties of marble could be divided into three different stages by corresponding critical temperatures of 300℃ and 600℃,at which heat damage factors are 0.29(0.30)and 0.88(0.92)in VE(AE),respectively.The thermal damage developes more fully in AE than in VE.The thermal environment plays an important role,especially in Stage 3.Specifically,a conspicuous difference(greater than 20%)between AE and VE occurs in corresponding dynamic strength and the anti-deformation capacities of tested marble specimen.The influence of heat damage of rock is very important and valuable in engineering practice,particularly when the temperature is very high(greater than 600℃).
基金Project(2005BA639C) supported by the National Science and Technology Development of China
文摘The kinetic behavior of leaching copper from low grade copper oxide ore was investigated. The effects of leaching temperature, H2SO4 concentration, particle size of crude ore and agitation rate on the leaching efficiency of copper were also evaluated. And the kinetic equations of the leaching process were obtained. The results show that the leaching process can be described with a reaction model of shrinking core. The reaction can be divided into three stages. The first stage is the dissolution of free copper oxide and copper oxide wrapped by hematite-limonite ore. At this stage, the leaching efficiency is very fast （leaching efficiency is larger than 60%）. The second stage is the leaching of diffiuent copper oxides, whose apparent activation energy is 43.26 kJ/mol. During this process, the chemical reaction is the control step, and the reaction order of H2SO4 is 0.433 84. The third stage is the leaching of copper oxide wrapped by hematite-limonite and silicate ore with apparent activation energy of 16.08 kJ/mol, which belongs to the mixed control.
基金Project(2016YFB0300802)supported by the National Key Research and Development Program of China。
文摘The effect of Li(2.0 wt%)addition on mechanical properties and ageing precipitation behavior of Al-3.0 Mg 0.5 Si was investigated by tensile test,dynamic elasticity modulus test,scanning electron microscopy(SEM),transmission electron microscopy(TEM)and high-resolution transmission electron microscopy(HRTEM)images.The results show that the tensile strength of the Li-containing alloy can be significantly improved;however,the ductility is sharply decreased and the fracture mechanism changes from ductile fracture to intergranular fracture.The elasticity modulus of the Li-containing alloy increases by 11.6%compared with the base alloy.The microstructure observation shows that the Li addition can absolutely change the precipitation behavior of the base alloy,andδ′-Al_(3)Li phase becomes the main precipitates.Besides,β′′-Mg_(2)Si andδ′-Al_(3)Li dual phases precipitation can be visibly observed at 170℃ ageing for 100 h,although the quantity ofδ′-Al_(3)Li phase is more thanβ′′-Mg_(2)Si phase.The width of the precipitate-free zone(PFZ)of the Li-containing alloy is much wider at the over-ageing state than the base alloy,which has a negative impact on the ductile and results in the decrease of elongation.
基金Projects(52075166, 51875197) supported by the National Natural Science Foundation of ChinaProjects(2019RS2064,2019GK5043) supported by the Science and Technology Planning Project of Hunan Province,China。
文摘The effect of T6I6 treatment on the dynamic mechanical and microstructure behaviour of Al-Si-Mg-Cu cast alloy was investigated using split Hopkinson pressure bar(SHPB), transmission electron microscopy(TEM), and highresolution transmission electron microscopy(HRTEM). Besides, the impact resistances of T6I6 and T6 motor shells of new energy vehicles made of Al-Si-Mg-Cu cast alloy were compared using a trolley crash test. The results indicated that the main strengthening-phases of the T6 peak-aged and T6I6 peak-aged alloy were GP zone and β″ precipitates. T6I6treatment can increase the density and size of β″ precipitates in peak-aged alloy and enhance both its tensile strength(σb)and elongation(δ). The dynamic toughness values of T6I6 samples are 50.34 MJ/m^(3) at 2000 s^(-1) and 177.34 MJ/m^(3) at 5000 s^(-1) which are 20% and 12% higher than those of T6 samples, respectively. Compared with a T6 shell, the overall deformation of T6I6 shell is more uniform during the crash test. At an impact momentum of 3.5×10;kg·m/s, the T6I6shell breaks down at 0.38 s which is 0.10 s later than the T6 shell.
基金Project(51479048) supported by National Natural Science Foundation of China
文摘Effects of strain rate and water-to-cement ratio on the dynamic compressive mechanical behavior of cement mortar are investigated by split Hopkinson pressure bar(SHPB) tests. 124 specimens are subjected to dynamic uniaxial compressive loadings.Strain rate sensitivity of the materials is measured in terms of failure modes, stress-strain curves, compressive strength, dynamic increase factor(DIF) and critical strain at peak stress. A significant change in the stress-strain response of the materials with each order of magnitude increase in strain rate is clearly seen from test results. The slope of the stress-strain curve after peak value for low water-to-cement ratio is steeper than that of high water-to-cement ratio mortar. The compressive strength increases with increasing strain rate. With increase in strain rate, the dynamic increase factor(DIF) increases. However, this increase in DIF with increase in strain rate does not appear to be a function of the water-to-cement ratio. The critical compressive strain increases with the strain rate.
基金Projects(51708377,51678311)supported by the National Natural Science Foundation of ChinaProject(BK20170339)supported by the Natural Science Foundation of Jiangsu Province,China+6 种基金Project(2016M591756)supported by the China Postdoctoral Science FoundationProject(17KJB560008)supported by the Natural Science Fund for Colleges and Universities in Jiangsu Province,ChinaProject(1601175C)supported by the Jiangsu Planned Projects for Postdoctoral Research Funds,ChinaProject(2016ZD18)supported by the Jiangsu Provincial Department of Housing and Urban-Rural Development,ChinaProject(2016T05)supported by the Jiangsu Provincial Transport Bureau,ChinaProject(2017A610304)supported by the Natural Science Foundation of Ningbo City,ChinaProject supported by the Bureau of Housing and Urban-Rural Development of Suzhou,China
文摘The desorption test was conducted to evaluate the desorption behavior of Pb(Ⅱ)and Cd(Ⅱ)using citric acid.The influential factors that were considered included initial Pb(Ⅱ),Cd(Ⅱ)contamination levels in soil,concentration of citric acid,reaction time,soil pH value and ionic strength.The test results indicated that the desorption was a rapid reaction(less than 6 h),and the removal percentages of Cd(Ⅱ)and Pb(Ⅱ)increased with the increasing contamination levels,concentration of citric acid and the addition of Na^+,Ca^(2+),Na^+, Cl~– and the chelating of organic ligands.
基金Projects(611061006,61073187) supported by the National Nature Science Foundation of China
文摘To improve the performance of chaotic secure communication,three simplified chaotic systems with one variable parameter were investigated.Basic properties were analyzed including symmetry,dissipation and topological structure.Complex dynamical behaviors of the systems including chaos and periodic orbits were verified by numerical simulations,Lyapunov exponents and bifurcation diagrams.Interestingly,the three systems were integrated in a common circuit,and their dynamical behaviors were easily observed by adjusting regulable resistors R28,R14 and R17,respectively,and the relations between the variable resistor and the system parameter were deduced.The circuit experiment results agree well with the simulation results.Finally,a secure communication scheme based on chaos shift keying(CSK) was presented,which lays an experiment foundation for chaotic digital secure communication.
基金Project(50905142) supported by the National Natural Science Foundation of ChinaProject(2009JQ1006) supported by the Natural Science Foundation of Shaanxi Province,China
文摘Composite wing static aeroelasticity was analyzed through a loosely coupled method and the effects on composite wing characteristics under different flight attitudes were presented. Structural analysis and aerodynamic analysis were carried out through finite element method (FEM) software NASTRAN and computational fluid dynamics (CFD) software FLUENT, respectively. Correlative data transfer and mesh regenerate procedure were applied to couple the results of computational structure dynamics (CSD) and CFD. After static aeroelasticity analysis under different flight attitudes, it can be seen that lift increases with the increase of flight speed and the incremental value enlarges gradually in both rigid and elastic wings. Lift presents a linear increment relationship with the increase of attack angle when the flight speed is 0.4Ma or 0.6Ma, but nonlinear increment in elastic wing when flight speed is 0.8Ma. On the effect of aeroelasticity, the maximum of deformation increases with the increase of flight speed and attack angle, and the incremental value decreases with the increase of flight speed while uniform with different attack angles. The results provide a reference for engineering applications.
基金Projects(51174094, 51101059) supported by the National Natural Science Foundation of China
文摘The glass formation was intensively studied for Fe-based alloys. Parameters defining kinetics and thermodynamic behavior of crystallization were calculated using calorimetric measurements and physical properties of constituent elements. It is found that the critical cooling rate Rc estimated by combining kinetic and thermodynamic parameters highly correlates with measured Rc found in literatures with correlation coefficient R2=0.944, and alloy compositions with high melting enthalpy AHm can easily form glass even without high undercooling and high value of the ,β-parameter of Tumbull＇s theory, revealing that the glass formation in this group of alloys is mostly controlled by growth limitation. This combination of kinetic and thermodynamic parameters can be used to determine alloy composition with good glass forming ability in Fe-based alloys just using physical properties of alloying elements and calorimetric measurements.
基金Project(2006AA09Z235)supported by the National High Technology Research and Development Program of ChinaProject(CX2009B003)supported by Hunan Provincial Innovation Foundation For Postgraduate,China
文摘Autonomous underwater vehicles （AUVs） navigating on the sea surface are usually required to complete the communication tasks in complex sea conditions. The movement forms and flow field characteristics of a multi-moving state AUV navigating in head sea at high speed were studied. The mathematical model on longitudinal motion of the high-speed AUV in head sea was established with considering the hydrodynamic lift based on strip theory, which was solved to get the heave and pitch of the AUV by Gaussian elimination method. Based on this, computational fluid dynamics （CFD） method was used to establish the mathematical model of the unsteady viscous flow around the AUV with considering free surface effort by using the Reynolds-averaged Navier-Stokes （RANS） equations, shear-stress transport （SST） k-w model and volume of fluid （VOF） model. The three-dimensional numerical wave in the computational field was realized through defining the unsteady inlet boundary condition. The motion forms of the AUV navigating in head sea at high speed were carried out by the program source code of user-defined function （UDF） based on dynamic mesh. The hydrodynamic parameters of the AUV such as drag, lift, pitch torque, velocity, pressure and wave profile were got, which reflect well the real ambient flow field of the AUV navigating in head sea at high speed. The computational wave profile agrees well with the experimental phenomenon of a wave-piercing surface vehicle. The force law of the AUV under the impacts of waves was analyzed qualitatively and quantitatively, which provides an effective theoretical guidance and technical support for the dynamics research and shape design of the AUV in real complex environnaent.
